The present invention relates to rotary reactors and, more particularly, to rotary reactors utilizing sand or other granular materials as a vehicle to accelerate the heating of the constituents to be burned therein.
Reactors, which include incinerators and retorts, incorporate hot sand in order to convey heat energy to the material being burned within the reactor. Such material may vary from oil shale to hazardous waste material having organic components. In order to convey the heat energy from the sand to the material to be burned, it is desirable to intimately mix the material with heated sand. Accordingly, certain types of these reactors include a mechanically-activated, "fluidized" bed for mixing sand. The mechanical component comprises a plurality of lifters attached to the reactor wall for conveying sand from a lower portion of the reactor to an upper portion, then dumping the sand in cascade-fashion back to the lower portion. In cascading, the sand becomes heated by contact with the burner flame and heated air within the reactor, and further contacts the material to be burned.
An example of such a reactor is disclosed in Taciuk U.S. Pat. No. 4,285,773. That patent discloses a reactor for the recovery of bitumen from rocks or sands and includes a horizontal, rotary reactor chamber having both flat-faced and cup-faced lifters bolted to the inner surface of the reactor chamber.
Similarly, O'Connor U.S. Pat. No. 4,066,024 discloses a rotating fluidized bed combustor having a cylindrical drum fitted with a plurality of baffles which extend longitudinally along an inside surface of the drum and sweep through a sand bed, located in the bottom of the drum, as the drum rotates. The baffles lift the sand from the bed, then drop the sand through an open region of the drum as the baffles rotate over the bed.
Typically, the bolts attaching the lifters of such reactors extend through the refractory lining of the rotary chamber, the chamber wall itself, and include a threaded portion protruding from an outer surface of the chamber. The bolts include heads which cam against a wall of the lifter and are secured to the reactor chamber by nuts.
A disadvantage with this mounting method is that gaps form between the the lifters and the refractory wall and collect contaminants. The exceedingly high temperatures within the reactor, the corrosive atmosphere and the abrasive nature of the material within the reactor cause the lifters to become separated from the refractory lining and to warp. In addition, thermal expansion of the lifters, caused by the extreme changes in temperature occurring within the reactor, cause stresses to be applied against the mounting bolts. These factors operate to shorten the life of a particular lifter and its associated attachment assembly, requiring undesirable downtime of the reactor for maintenance and repair. Accordingly, there is a need for a lifter attachment assembly which is capable of withstanding the corrosive environment within the reactor and of accommodating the thermal stresses imposed on the lifter and lifter attachment assembly.